Manufacture of sulphamic acid



Patented Oct. 1, 1946 r MANUFACTURE OF SULPHAMIC ACID Ernest Tauch. Cleveland Heights, Ohio; as-

V signor to E. I. du Pontde Nemours & Company, Wilmington, Del., a corporation 'ofxDelaware No Drawing. Application January 8, 1943, Serial No. 471,743

This invention relates to the maniacture of sulphamic "acid and is directed to processes in which urea, sulphuric acid and sulphur trioxide are brought together in the proportions which on subsequent conversion to sulphamic acid give a dry product and converted to sulphamic acid in the presence of a solid pulverulent diluent under conditions that no substantial continuous body of liquid is present during the conversion, and more particularly to processes in which the reagents are brought together in the stated proportions and converted to sulphamic acid by heating whilei'the reaction component is kept dispersed in or on the surface of a'solid pulverulent diluent.

This application is in part a continuation of my copending application Serial No. 356,359 filed September 11, 1940, and incorporates herein by reference all the subject matter of that application and contains subject matter in common with my copending application Serial No. 356,358 filed September 11, 1940. I

Prior to these applications the art had not known how to produce sulphamic acid from urea,

sulphuric acid andsulphur trioxide directly as a dry free-flowing product and had not conceived it possible to do so. Rather, the art has heretofore found it necessary to produce sulphamic acid from these products by the so-called wet process in which the sulphamic acid is produced as a slurry in sulphuric acid. Said processes are subject to'a great many difiicuties some of which arise in filtration, centrifuging or settlingothers "of which in corrosion problems brought about by the many different strengths of sulphuric acid involved, still others in the decomposition of the sulphamic acid brought about by the heat gen erated in diluting sulphuric acid in washing the crystals of sulphamic acid, and still others of which appear as limitations on throughput.

, Now I have found that sulphamic acid can be produced directly as a drypulverulent product without being subject to any of these difiiculties by bringing together the urea, sulphuric acid and sulphur trioxide in the proportions which on subsequent conversion to sulphamic acid gives a dry product and converting to sulphamic acid in the presence of a solid pulverulent diluent under conditions such that no substantial continuous body of liquid is present during the reaction and preferably by heating while the reaction component 8 Claims. (01.23-166) ized and remarkable economies are achieved. Thus the product is produced directly as a dry,

. free-flowing mass; the proceses are excellently is kept in a dispersed condition in or on the sur- 'face of a solid pulverulent diluent;

suited to be used as continuous rather than intermittent for batch operations, and for this reason the economic advantages arising .from continuous operation can be realized. The. disadvantages pointed out above are; avoided and greater throughput. is possible. Whether the processes are used as continuous; intermittent or batchoperations they have the iurther advantage of being free of dan'ger of thereaction proceeding at an uncontrollable rate ;by maintaining the liquid component of the sulphamic'acid formi'ng reaction dispersed in or upon the surface of'a solid pulverulent diluent whereby no continuous body of liquid is present during. the sulphamic acid-forming reaction, barriers are imposed to the self-propagationoi the reaction, greater surface area is provided for the liberation of; the gaseous product of the reaction and more complete and uniform temperature control can be effected. t Q

In carrying out'the processes of my invention the reactants maybe brought together in a variety of ways and the method of effectingthe dispersion may be varied as may be'best suited to any particular. way; The sulphur trioxide and sulphuric acid may be added together as oleum of various strengths or separately as gaseous or containing component may be added to the urea slowly and in a manner such that dispersion of the liquid upon the surface of the urea as films or droplets is effected. The urea may be'di's solved in o-r'reacted with the sulphuric'acid and the resulting product brought in contact with oleum of suitable strength. Similarly urea and sulphur trioXide might be pre-reacted and brought in contact with sulphuric acid, One particularly attractive methcid involves'p'remixing of all three reactants under suitable controlled conditions to give an intermediate product of liquid form, as is taught in the 'co-assigned 'application Ser. No. 509,276, and thereafter effecting the sulphamic acid-forming reaction while the product is in a suitably dispersed state. Whatever the particular manner of bringing together the reactants the particular mode should- :be selected with the view of dispersing the reaction component 'of the sulphamic acid-forming reaction in or upon the surface of a solid pulverulent diluent whereby no substantial continuous body of liquid is present during that reaction and the reaction is efiected with the reaction component dispersed upon the surface of a solid pulverulent diluent.

The condition that substantiall no continuous body of liquid be present is to be understood to meanthat any liquid component which .is present exists in a substantially dispersed condition. The liquid component referred to might be, for instance, sulphuric acid, oleum, or a solution or slurry of the reactants or reaction products or intermediate products in the sulphuric acid or oleum, or a premix intermediatereaction ;prodnot, the latter product being --a liquid component which may be prepared according to the teachings of the co-assigned application Ser..:No.

The presence of a substantially con- 509,276. tinuous body of liquid due to such liquid 1components may be avoided by effecting dispersion of the liquid into .such forms .as small droplets or films. It is observed that ,films .do not constitutea continuous body of liquid because .theyare substantially discontinuous in one dimension. The reaction componentis to be understood to meanthat partof the mass.inwhichthesulphamic acid-forming reaction takes place. It is thatpart which is converted to ,sulphamic acid in the reaction. .Itisinherentlyliquid but in the processes .of my invention rapidly dries up as sulphamic acid is formed. The reaction .mass as disting-uishedfrom the reaction component may beap- ,parently drybecause of the dispersion of the reaction component .(liquid) on the surface of the particles'of .pu'lverulen't solid. .It. is believed that such dispersion, especially under optimum conditions, is in the .formof .a film on the surface of these particles though it is to be understood that .it may be asdroplets orsmall bodies of discontinuous liquid throughout the interstices of the pulverulent mass.

In order to, initiate reaction a temperature consistent with the formation of sulphamic acidmust be involved. When the reagents are brought together .heat must be applied over and above normal temperatures either through the reactants themselves or to the reaction mixture in .order that .a temperature willobtain which is conducive .to the formation of sulphamicacid. The reagents may be brought together at this temperature by .preheating ,or .by introducing them into a heated zone, or they may be premixed with cooling sumcient to inhibit the formation of sulphamicacid and the premix product heated to the desired temperature, processes of the latter method being taught in the co-assigned application Ser. No. 509,276. supplied initially to cause the formation of sulphamic acid to proceed at a practical rate. It

'is satisfactory to maintain a temperature above "about 150 F. for this purpose. At temperatures above about 150 F. the reaction is likely to be self-propagating unless the precautions previously set out are'observed. Even when such-con- 'ditions are observed inferior results are likely to be obtained in view .of the temperatures becoming too high. Insuch case "decomposition products .such asammonium bisulphate are likely to predominate. For practical purposes itis well to keep the-temperature below about 250 F. By effecting .suitableqcontrol of the temperature of the dispersed reaction component during the reaction -I am-enabled to avoid undesirable iby-product .formation and at the same time .so to regulate the rate of the reaction that, coupled With the In any case suflicient heat must be barriers against self-propagation, the reaction proceeds smoothly and simply Without hazard of explosion or other difficulty. Thus in the processes of my invention it is desirable to maintain the temperature within the limits of about 150 1 to about 250 F. and to do it in such a way that .any desired temperaturewithin' these limits may diluent ina suitable state of agitation in order to .effect and maintain dispersion of the reaction component of the sulphamic acid-forming reaction on the surface of the particles of diluent, it is possible continuously to bring these individual particles in contact with a suitably cooled surface, as, .for example, internally cooled mixer arms or water jacketed Walls of asuitable mixer. .In this manner the reaction component of the sulphamic acid-forming reaction .iscaused to film .out over the surfaceof. a temperature-controlled solid in a finely divided .orpulverulent stateand the temperature-controlled solid thus acts as a transfer medium for transferring theheat of the reaction from the .reactingmedium to the cooled surfaces and also as to reservoir to absorb heat of the reaction .andprevent local overheating. The solid .pulverulent diluent also acts as the heating means to bring the .reaction component to a reactive temperature. It is .of particular advantage in this respect in that it rapidlybrings it to the desired temperature and keeps it there. In this manner I am .able effectively to carry out the conversion to sulphamic acid without danger .of .self-propagation, local overheating or the disruptive effects of violent liberation of carbon dioxide.

The advantages of my invention are most fully obtained if the'dispersion is so complete that the 1 reaction mass remains apparently 'dry and pulverulent throughout the reaction.

It is desirable therefore to effect the dispersion in a relatively large mass of pulverulent diluent, that is, relatively large as-compared with the reaction component. It .is desirable, by suitable mixing, to effect'a uniform dispersion of the reaction component in the mass, that is to say, throughout any portion of the mass but not necessarily throughout the wholeof the mass. Itwill be understood that if the reaction component is 'dispersed on the surfaceof 1a pulverulent diluent, that is,-on the surface-of the particles of that diluent, the dispersion inherently is uniform and the mass of diluent is inherently substantially greater than the mass of the reaction component.

In the broader aspects of my invention, however, a lesser degree of dispersion is contemplated and is permissible so long as the limiting condition is observed that no substantial continuous body of liquid is present in the reaction mass.

,knowledge apart from the wet processes.

my invention that I. am ablelto carry-out the reaction substantially in'these proportions'tor, youmight say, in proportions such that lutimately stoichiometric proportions .are present together with such variations from the stoichio metric proportions as do not bring about the for mation of a final productwhich is wet. If substantially stoichiometric pro-portions are employed under the conditions of my'invention as explained above, the product obtained is not excessively wet. a 1

It will be understood that sulphur trioxide may be dissolved in sulphuric acid to form oleum and that oleum may be used in the reaction, a 65 per cent oleum, for instance, containing 65 parts by weight of free sulphur trioxide dissolved in 35 parts by weight of 100 per cent ulphuric acid. When a 65 per cent oleum is used it isnecessary, in order to have present stoichiometric proportions, to use sufiicient free sulphuric acid to give a total sulphuric acid: sulphur trioxide weight ratio of 98:80. a A 45 per centoleum contains Sulphur trioxide and sulphuric acid inapproximately stoichiometric proportions for the purposes of the processes of our invention. A 45-50 per cent oleum is particularly suited to the .formation of a dry product when used in the com bining proportions with urea, i. e., mole for mole figured on the urea and the sulphuricacid. The excess sulphur 'triox ide does not interfere, with the formation of a dry product for reasons to be pointed out hereinafter and in some cases is. beneficial in accelerating the reaction.

In an illustrative embodiment of my invention sulphamic acidis produced from urea, sulphuric acid and ulphur trioxide by effecting contact between the reactants in the presence of a solid pulverulent diluent at a temperature of from about 150 to 250 F. under the limiting circumstancethat the liquid component containing the sulphuric acid is maintained in sucha state of dispersion that substantially no continuous body, of liquid is present during the reaction. Within this limiting circumstance variation of the separate conditions such as rate of addition and intensity of mixing the reactants is possible. Thus, if the temperature in the mixing zonefis held at about 150 to 250 F. and intensive mixing is provided, the reactants can be added to one another as relatively large increments, and it i not essential, though preferable, that the increments be in stoichiometric proportion, at all times, provided that conditions otmixing are such that substantially no continuous body" of liquid is present after contact of the reactants in the presence of the diluent. Conversely, if the temperature is similarlycontrolled and'the reactants are added to one another as small stoichiometrically equivalent increments, and the amount of solid pulverulent diluent is large relative to the amounts of reactants, less intensive mixing ordinarily will be required to prevent the presence of a continuous body of liquid after conta'ct of the reactants. V f

In order that the nature of my novel processes may be more clearly described, referencewillbe made hereinafter, by way of example, to specific embodiments of the processes, but it will be apparent that many variations and modifications I may be made in the particular conditions set forth. The parts are by weight unless otherwise specified. Example I, which follows, illustrates a process of my invention in which urea, sulphur trioxide, and sulphuric acid are caused'to react at a controlled temperaturein the presence of a 6 solid pulverulent idiluent ,under mixing condttions suchthat the presence of a continuous body of liquid in the mixing zoneis "avoided. s

Ert'izmple I j Into a jacketed ough mixer equipped with sigma-shaped mixing arms there was placed 50 parts of a crude grade of dry, granularsulphamic acid, containing approximately 82 per cent sulphamic acid, 13 per cent ammonium bisulphate, and per cent-sulphuric acid, to act as a diluent for the reactants subsequently to be used. Urea, oleum, and sulphuric acid were then added simultaneously,but from separate sources, to :the mixer, agitation of the mass in the mixer being provided by rotating the mixing arms. additions were made as substantially .stoichiometric equivalent increments, the rate of addition being 0.75 part 'of urea, 2.0 parts of .65'per cent oleum, and 0.5 part of 98 per cent sulphuric acid every l5minutesover a period of five and one-quarter hours, and the addition of each increment being approximately continuous over the 15-minute period. The temperature of the reaction mixture was maintained in the range from 173 to 195 F. by passing cooling water at a suitable rate through the mixer jacket. The reaction mixture, remained at all times a stirrable', free-flowing mass. After' five and one-quarter hours the addition of reactants was stopped, there having been added a total of 15.75 parts of urea, 42 parts of 65 per cent oleum, and 10.5 parts of 98 per cent sulphuric acid. Agitation was-continued for an additional three-quarters of an hour to insure complete reaction before the product was discharged from the mixer.

- There was obtained 100 parts of a granular, a

free-flowing, light-colored product. which was shown by analysis to have the approximate composition of the crude acid originally used as a diluent, namely, about 82 per cent sulphamic acid, 13 per cent ammonium bisulphate, and 5 per cent'sulphuric acid. This crude product was purified by recrystallization from water, whereby its sulphamic acid content was raised to 98 per cent.

The foregoing example illustrates the application of a process of my invention as a batch operation. By a suitable choice of equipment and 5 manner of adding the reactants the operation may be made continuous. In Example II, which simulates continuous operation with respect to the product in the reaction chamber, it is shown that the composition of the product does not vary substantially even though portions of the product are intermittently discharged and replaced by additional product formed by the reaction.

Example II This example was carried out in the same equipment as used in Example I.

. The proportions of urea and oleum used were calculated so as to give a 15 per cent excess of sulphur trioxide, in the form of oleum, over that These '7 simultaneously added, .over 15-minute intervals, 3.0 :parts of urea, 11.92 parts of 98 per cent 'sulphuric acid, and 7.33 zpartsoi 65 per cent oleum. Continuous, intensive mixing was provided and the mixture was held at about 200 F. by proper control of cooling water in the jacket of the reaction vessel. The reaction mixture remained at all times a dry, .pu'lverulent, free-flowing mass. After one and one-quarter hours the addition of reactants was suspended, the product in the mixer was agitated for an additional one-quarter hour, and a portionof theproduct-amounting to 50 parts by Weight 'was discharged from the mixer. Addition of reactants was then resumed and continued for another one and one-quarter hour period. A further one-quarter "hour of '-mixing was allowed, after which an additional BO-parts by weight of product was discharged I-from the mixer. This process was repeated for three more like periods.

The composition of the product discharged after the first reaction period was found 'to be approximately 74.2 per cent sulphamic acid, 233 per cent ammonium 'bisulphate, and 2.5 per cent sulphuric acid, while after the fifth reaction period the composition :Was approximately 77.0 per cent sulphamic acid, 16.4 per cent ammonium bisulphate, and 6.6 percent sulphuric acid.

.It 'will be seen from Example II that the sulphamic acid content of the product made according 'to a process of my inventionis at least as high after a period of substantially continuous operation as it is afterasingle batch is produced.

Hence .the practicability of continuous operation is o bvious.

In the "following example there is illustrated theigreat potentiality of the invention 'for the continuous production of sulphamic acid on a large scale.

Example III A heel of approximately 80041001) lbs. of crude sulphamic acid-was :added to .a .300 gallon Read Sigma Arm dough mixer equipped a water jacket and hollow arms through which mold-water was circulated for cooling. The heel first heated by means of steam .on :the jacket to a temperature of not less than 16TH. Then urea and 5 8.0% oleum were fed simultaneously and continuously at rates of .18 lbs. of urea per minutes and 58 lbs. of oleum .per 15 minutes with 210,000 lbs. of water per 24 hours ates passing through the jacket andarms. The temperature .of the reaction mass in themixerwasmaintained at 220 to 240 :F. Theproduct was discharged from the mixer intermittently by'.opening the discharge gate at intervals and'jallowing the product to flow out. In 24 hours there was produced 5,600 lbs. crude su'lfamic acid containing 81% NHzSOsI-I.

The following is illustrative of another type of process in which my invention is embodied and shows still greater potentialities of increased throughput.

Example Y V One hundred and seventy-one pounds of 54.5% oleum was charged in. a premixer. and there agitated and cooled by continuously circulating it through an internal cooler. Urea was gradually added in small "increments while maintaining a temperature of about 100F. until'do'pounds of urea was added. Thereafter urea and 54. 5%

oleum were added substantially-in theproportions of one mole of urea for each mole of sulphuric acid at a rate of about 120 pounds total ingredientsiperhour. This product was introduced into .a.'20-gallon.Read Sigma .Arm dough mixer filled to about 10% of its capacity with crude sulphamic acid while maintaining a temperature of about 220.iF. In a period of one hour during which :periodic withdrawals were made as required, there was produced ISO-pounds of sulphamic acid having an average analysis of 90.0% sulphamic acid, 9% ammonium bisulphate and 1 sulphuricacid.

While sulphamic acid products,-suc'h as that o'fExample II, containing ammonium bisulphate and sulphuric acid as impurities are suitable for 'many uses, it may be desired to remove these impurities so as to obtain substantially pure sulphamic acid. "By suchexpedients as providing extremely-intensive mixing of reactants and carefully dispersing the oleum and urea as they are added .to each other in'the presence of an inert diluent, I have found that the presence of impurities in sulphamic acid prepared by a process of my invent-ion can be confined -to a minimum. -On a large scale, how-ever, it may be preferable in somecircumstances to carry out the processes under condition-swhich do not "entirely avoid con- 'tamination of the product, and subsequently to purify the product by suitable methods.

Such purification can readily be accomplished -by dissolving the im-pure product in Water and recrystallizing it according to conventional practices. However, the solubility of sulphamic acid is not greatly increased with an increase in temperature; hence, the usual methods of crystallizing, involving cooling a concentrated solution to 'a reduced temperature, are not as effective as -might be wished. I have found that the ,im-

purities ordinarily occurring in sulphamic acid can be effectively removed by alternately heating and'cooling a slurry of the product in an amount of 'water insufiicient completely to dissolve the sulphamic acid and thereafter removing the sulpham'ic acid as crystals from the resultant mother liquor containing the dissolved impurities. By such aprocedure, not only are the impurities taken into solution without the necessity of .com-

pletely dissolving .the sulfamic acid, but also the size .of the "sulphamic acid crystals is increased so thatithe mother liquor can readily be drained or ,filtered off, whereas without the alternate heating and cooling steps, the fineness of the crystals would causedifliculties in. such draining or filtering operations. Thus, by .slurrying 'partsby weight of the product of Example II in 100 parts of water and holding the slurry for one hour in a tank heated by suitable means in the center-and cooled by suitable means around the outside, the impurities in the product were taken into solution while the sulphamic acid was, for the most part, left undissolved. The mother 'liquorso formed was readily removed by filtration and a 'dry sulphamic acid ,product was obtained having a purity of more than .98 per cent sulphamic acid.

While my novel processes for producing sulphamic acid have been described with particular "relation to the foregoing examples, the particu "lar conditions of. these examples are susceptible to'considerable variation and modification.

It is desirable to effect dispersion of theliguid components in aprocess of 'my invention by intensive'mixine prior to or at the point of contact of the liquid with the other reactants and with the solid pulverulent diluent. The choice of methods 'for securing such a dispersion depends to some extent upon the form in which continuous body of liquid after contact of all pulverulent diluent. n V

The apparatus used for mixing the reactants the reactants with each ether and with the in a process of my invention; preferably should be capable of maintaining the reaction mixture at all times as a substantially -solid,;fr eeflowing pulverulent mass with substantially no continuous-liquid phase present after contact of the reactants with each other and with the diluent. For this purpose eequipment of the type commonly used for stirring dry or plastic materials conveniently may be used. The dough mixer shown in the foregoing examples is well suited to the task as are also such mixing devices as chaser or edge runner mills, pug mills, heavy duty ribbon blenders, scraping blade kettles of the Dopp type, andgraining bowls. Other suitable mixing devices will be readily apparent to those skilled inthe art.

In the processes of my invention the urea, sulphuric acid, and sulphur trioxide. or their equivalents preferably are used insuch proportions that substantially molecularly equivalent quantities are ultimately present; that is, for each mole of urea there isused one mole of sulphuric acid and one moleiof sulphur trioxide. The proportion of sulphur trioxide used may be somewhat in excess of the calculated proportion theoretically required, since carbon dioxide is evolved during the reaction and a portion of the sulphur trioxide present may be carried off with this evolved carbon dioxide. Furthermore, a portion of the sulphur trioxide may become hydrated to sulphuric acid by moisture present in the reactants and in the atmosphere of the mixing zone.

Thus, under the conditions of the foregoing Ex ample II, a per cent excess of sulphur trioxide was employed to advantage. In any event, the amounts of excess used should not be so great as to cause the reaction mixture to become pasty but little difficulty isencountered with any excess because sulphur trioxide is highly volatile at the temperatures of the reaction.

As has already been indicated above, the reactants may be simultaneously added to the reaction zone in substantially theoretical proportions. However, under some circumstances it may be preferable first to effect reaction between solid diluent, or indeed may itself function as a' solid diluent, and the sulphur trioxide and sulphuric acid may be added'increment-wiseto this solid with suitable agitation.-

The solid diluent used in the processes of my.

. ammonium bisulphatepresent in the diluent, the

presence of this compound appearing to prevent or retard: the formation of. further amounts of ammonium bisulphate' as an impurity. Moreover, if-the presence of ammonium bisulphate in the reaction product is not objectionable, it may be usedin the diluent whether or not a recrystallization or washing step is subsequently used. Similarly, if the product is to be used in conjunction with other materials, these other materials if suitable may be used as diluents. Thus, if the product is intended for use as a fire retardant, the solid diluent may be an inert material which is a suitable ingredient for fire retardants such as diammonium phosphate.

The amount of diluent will necessarily depend on the nature, and type of mixing employed, but in any event the amount should be substantial relative to the amounts of liquid reactants present. It is usually preferable to use such an amount of diluent that the most efiective use is made of the apparatus provided without exceedingthe maximum allowable temperature for the reaction. As the product is'formed it serves to act as, the diluent, and hence during the course of the reaction the amount of diluent may be successively reduced as new product is formed. A wei ht of diluent equal tofrom'about 10 to- 20 times the weight of the reactants present is representative of the proportions which may be used satisfactorily, but it will be understood that these proportions are only indicative of a range and that observation of a few simple tests made under the condition which it is proposed to use will readily permit one to determine a suitable proportion of diluent to reactants in a particular set of conditions.

The processes of my invention are particularly well adapted for use when-the sulphamic acid product is to be converted to its salts since such conversion may often be advantageously carried out in the sameapparatus as used in the manufacture of the acid. Thus, when it is desired to obtain ammonium sulphamate, ammonia gas may be admitted to the reaction chamber after the preparation of the acid has been completed as above described, and ammonium sulphamate may be produced ina dry way simply by continuing the agitation.

While I have shown certain specific processes in the foregoing disclosure, it will be understood that one skilled in the art may readily employ numerous processes Without departing from the spirit of this invention.

I claim:

1. In a process for the manufacture of sulphamic acid from urea, sulphuric acid, and sulphur trioxide, the step of adding the components of the reaction, urea, sulphuric acid, and sulphur trioxide, at such relative rates while mixing with a solid pulverulent diluent that the urea and sulphuric acid are present in the reaction mass in substantially the molar proportions of 1:1 and the sulphur trioxide is present in a molar proporatoms tion to the other reacting components' of not less than 1 :1" and so that the reaction mass remains apparently dry and Without the presence of any substantially continuous liquid phase.

a 2; In a process for producing sulphamic acid from-urea, sulphuric acid, and sulphur trioxide, the steps comprising adding urea, sulphuric acid, and sulphur trioxide to a solid particulate diluent andagi'tating the solid particulate diluent during the addition, the rate of addition being such that the reaction massremains apparently dry and particulate thruout the reaction.

3; In a process for producing sulphamic acid from urea, sulphuric acid, and sulphur trioxidc, the steps comprising adding urea, sulphuric acid, and-sulphur trioxide to a solid particulate sulphamic aci'd and agitating the sulphamic acid duringthe addition, the rate of addition being such that the reaction mass remains apparently d ryandparticulate thruout the reaction.

In a process for producing sulphamic acid from.urea-sulphuric acid, and sulphur trioxide, the steps comprising adding urea, sulphuric acid, and sulphur trioxide' to a solid particulate diluent maintained ata temperature of about l50-250 F. and agitating the solid particulate diluent during the additiomthe rate of addition being such that the reactionmassremains apparently dry and particulate th-rnout the reaction. 5';'In a'pro'cess for producing sulphamic' acid from urea, sulphuric acid, and sulphur trioxide, the steps comprising adding urea, sulphuric acid, and." sulphur trioxi'd'e to a solid particulate sulphamic acid maintained at ate'mperature o1 about 1 5.9-'0' F2 and agitating? the sulpha'mic acid duringthe' addition, the. rate of addition being such that the reaction mass remains apparently dry and. particulate thruout the reaction.

62. In a: process for producing sulphami'c acid from urea, sulphuric acid, andsulphur trioxide, the steps comprising" adding urea,- sulphuric acid, and sulphur trio-Xidetoa solidparticulate diluent comprising sulphamic acid and ammonium bisulphate, the diluent being maintained at a temperature of about 150-250F. and agitating the solid particulate diluent during the addition, the rate of addition being such that the reaction mass remains apparently dry and particulate thruout the reaction.

'7. In a process for producing sulphamic-aci-d from urea, sulphuric acid, and sulphur trioxide; the steps comprising adding urea, sulphuric acid, and sulphur trioxide substantially in the pro-portions of one mole of urea, one-mole of sulphuric acid, and atleast one mole of sulphur trioxide to a solid particulate sulphamic acid maintained at a temperature ofab'out ISO-250 F. and agitating thesulphamic acidduringthe addition, the rate-of addition being such that the reaction mass remains apparentlydry and particulate thruout the-reaction.

8 In a process for producing sul'pnamic acid fromurea, sulphuric acid, and sulphur'trioxide, the steps comprising adding urea and to 60%- o'leum toa solid particulate sulphamic acid maintain'e'd at-a temperature of about I-250 F. and agitating the sulphamic acid during'the addition, the strength of theol'eu-m and the proportions of olen-mto urea being regulated to provide-sulphur trioxide' in excess of that required'to combine with the urea and any water absorbed from the atmosphere while providing sulphuric acid in the reaction mass in substantially a mole for mole ratio with the urea and regulating the rate of addition so that. the reaction mass remains apparently-dry andparticulate thruout the reaction ERNEST J TAUCH. 

